Subramanian Ramakrishnan

We have examined the formation and dissolution of gels composed of intermediate volume fraction nanoparticles with temperature-dependent short-range attraction using small-angle xray scattering (SAXS), x-ray photon correlation spectroscopy (XPCS), and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically-determined gel temperature T_gel was characterized via the slow-down of dynamics observed in the intensity autocorrelation functions (g₂) as a function of quench depth (DT = T -T_gel), wave vector, and formation time (t_f). We find self-similarity in the slow-down of dynamics that maps the wave-vector-dependent dynamics at a particular DT and t_f to that at other DTs and t_fs via an effective scaling temperature, T_s. A single T_s applies to a broad range of DT and t_f but does depend on the particle size. The rate of dynamical evolution implied by the scaling is a far stronger function of DT than the attraction strength between colloids. We interpret this strong temperature dependence as collective particle motion possibly arising from rearrangements of energetically-favored locally structures observed in confocal microscopy and via simulations.

• Time: 11.00 AM
• Location: 206 Furnas Hall
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